Field Trials to evaluate fungicides for control of Phytophthora root rot of caneberries (raspberry)

Project Code SCR07-005

Project Lead

Janice Elmhirst - Elmhirst Diagnostics and Research

Objective

To evaluate under field conditions candidate fungicides for control of phytophthora root and crown rot of raspberry and to provide recommendations for possible minor use label expansion

Summary of Results

Root and crown rot caused by Phytophthora fragariae var. rubi causes serious crop loss each year to raspberry producers in British Columbia, Ontario, Quebec and the Maritimes.

In 2007, 14 fungicide product treatments were evaluated in container grown raspberry plants (see summary for Project SCR07-004). The most promisingproducts from this trial were further evaluated in the field the following year.

In 2008, ten fungicides were screened for potential to control Phytophthora root and crown rot of raspberry in field trials conducted in the Fraser Valley, British Columbia, Canada. Commercial bareroot raspberry plants cv. 'Malahat', highly susceptible to Phytophthora root rot, were planted in June, 2008 at a research site. Products were applied as soil-drenches at planting in 100 mL/plant in a randomized complete block design with 10 plants per plot and four replicates per treatment. Plants were inoculated 24 hours later with a recent BC isolate of Phytophthora rubi (from A. Muelchen, AAFC-PARC Agassiz) grown on V8 plates (final inoculum solution contained 0.5 x 06 zoospores/mL; 100 mL solution applied per plant). Treatments included a non-inoculated check. Plants were rated monthly for chlorosis, necrosis, dieback and symptoms of phytotoxicity.

After 16 weeks, plants treated with ranman (cyazofamid) at 0.25 L/ha + Sylgard 309 surfactant (0.15 L/ha) in 1000 L water/ha had the greatest foliar height and plant growth rating, followed by plants treated with ALLEGRO 500F (fluazinam) at 1.0 L/ha in 2000 L/ha. Plants treated with ranman + surfactant had the highest root dry weight and scored lowest for % root rot and crown rot, not significantly different from plants treated with allegro. Plants treated with either ranman + surfactant or allegro had the highest foliar fresh weight and plant growth ratings, with no phytotoxicity. Disease control with these two products was significantly different from the inoculated check in Tukey's HSD at P?0.05, for all parameters measured and was equal to or greater than that obtained with the standard, subdue maxx (metalaxyl-m).

Results from this project will support the implementation of new disease management solutions for raspberry growers in Canada.

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